CT of orbital trauma

In a patient with acute orbital trauma, visual acuity and extraocular muscle motility are the two most important ophthalmologic functions to be evaluated emergently. The assessment of these capabilities may sometimes be difficult due to the severity of the head injury, the extent of periorbital soft tissue edema, inadequate cooperation in alert patients, and a reduced level of consciousness in obtunded individuals. Consequently, computed tomography (CT) has come to play a major role in the orbital examination of acute trauma patients. In this study, in conjunction with clinical evaluation, we have sought to utilize CT to determine the various prevalences of the causes of decreased visual acuity and extraocular muscle motility resulting from orbital trauma. We retrospectively reviewed the records of all patients admitted to our emergency facility who, having suffered head trauma, underwent a CT study for diagnosis. CT examinations of the head using a multidetector scanner were performed from the base of the skull to the vertex at 5-mm intervals. Orbital CT was obtained when a routine CT of the head showed periorbital soft tissue edema and/or facial bone fractures. The orbital CT examination was performed using axial 1-mm and coronal 3-mm slices. Coronal reformation images were prepared if the patient was unable to tolerate the prone position for direct coronal imaging. The imaging findings were correlated with ophthalmologic observations. The orbit floor was the most common and the orbital roof the least common site of fracture of the bony coverings of the eye. Twenty-three patients suffered decreased visual acuity. In order of declining frequency, the causes of reduced vision consequent to trauma were retrobulbar hemorrhage, optic nerve thickening presumably secondary to edema, intraorbital emphysema, optic nerve impingement, detached retina and ruptured globe. Five patients had visual impairment without demonstratable radiographic abnormalities. The most common finding associated with diminished extraocular muscle motility was muscle impingement by fracture fragments, followed in decreasing frequency by thickened muscle due to edema or contusion, intraconal emphysema, muscle entrapment, and retrobulbar fat herniation. Six patients with decreased extraocular muscle activity had no abnormalities demonstrated on CT images. The overwhelming majority of patients with decreased visual acuity or reduced extraocular muscle motility consequent to trauma had abnormalities demonstrated by orbital CT. Hence, CT examinations should play a major role in the evaluation of the intraorbital contents in patients with orbital trauma.